This happened to me a while back. I bought some diapers from someone, the said they were original owners, only used a year, been stored for over a year so she washed and stripped them for the buyer. I got them in, washed them, and hung them to dry.
First diaper, her pants were wet within 30 min. (I had regular pants over the dipe.)
Second diaper, pants wet within an hour... This is when I knew something wasn't right. I figured I would try to strip them. I figured it couldn't hurt. First wash i added a little bit of blue dawn. The next 8 washes were as hot as possible. One night, I added some boiling water to the washer of hot water, added diapers, and let sit overnight. I finished the wash and dryer them for 30 min on med heat, then Hung them. It worked... These diapers are the bomb!!! They are my go to diaper on most days.
I was to a point where I was ready to throw them away, so this heavy duty stripping was my last option. I figure I couldn't hurt what I was going to throw away...
Hope something works for you.